1. Field of the Invention
This invention relates to an optical disk device for writing onto an optical disk to allow writing of invisible data whose record address is not registered in an address information area in which record addresses of written data are registered.
2. Description of the Related Art
Even if data recording is temporarily suspended, a writable optical disk such as a write once optical disk enables data recorded after the suspension to be integrated with the data recorded before the suspension. Thus, if data recording is temporarily suspended, the data recorded before the suspension is not registered in an area indicating data record information in track units, which will be hereinafter referred to as PMA (program memory area). This means that the data recorded before the suspension is data that cannot be referenced from PMA information, which will be hereinafter referred to as invisible data. Therefore, when writing is started, it needs to be executed from the end address of the invisible data and the last address of the invisible data needs to be known.
Thus, when a write instruction is given, the operation of detecting the last address of the invisible data is performed. That is, an address is found by making a binary search from the last address indicated in the PMA information and the last address of a user data area and whether or not data is recorded at the found address is determined. If data (invisible data) is recorded at the found address, continuous reading is started. When header information provided by the continuous reading indicates the end of the invisible data, the last address of the invisible data is found from the address of the end block.
The operation of finding the last address requires time of two to three seconds. Therefore, when writing is executed, the time to find the last address and the time to actually write data are required and the write speed slows down when viewed from the outside of the device.
On the other hand, related arts for shortening the write time by previously obtaining the write start address are proposed in Japanese Patent Unexamined Publication No. Sho. 59-146446 (first related art) and Japanese Patent Unexamined Publication No. Hei. 5-189868 (second related art). That is, in the first related art, detection means for determining whether or not data is recorded in each sector of an optical disk and storage means for storing information indicating whether or not data is recorded in a memory area related to each sector are provided. While writing is not executed, the presence or absence of data is detected for each sector and the detection result is stored in the storage means. Therefore, when writing is executed, whether or not data is recorded in the sector instructed to be written on is determined based on the information stored in the storage means and when data is not recorded, data is written. In the second related art, a volume name and last write address storage section is provided. At the termination of data writing, the last write address is stored in the volume name and last write address storage section. Therefore, the address at which the next writing is to be executed becomes one plus the last write address stored in the volume name and last write address storage section. Thus, the address at which writing is to be executed is found simply by adding one to the last write address stored in the volume name and last write address storage section. This means that the time to find the write address is extremely shortened.
However, the related arts introduce the following problems: In the first related art, while writing is not performed, whether or not data is recorded is determined for each sector and the determination result is stored in the storage means. On the other hand, an optical disk has a large storage capacity. Thus, if the capacity of one sector is lessened, the number of sectors becomes extremely large and therefore a wide area needs to be reserved as the memory area of the storage means. In contrast, if one sector is made a wide area for lessening the number of sectors to narrow the memory area of the storage means, the probability that a large empty area will occur in each sector becomes high and the use efficiency of the data record area lowers.
In the second related art, previously registered volume names and last write addresses are stored in a one-to-one correspondence with each other. At the termination of writing, the last write address is stored. Therefore, to write onto an optical disk containing no volume names registered in the volume name and last write address storage section, the stored last write address cannot be used. If even an optical disk containing a volume name registered in the volume name and last write address storage section is written on by a different device, the last write address stored in the volume name and last write address storage section is not updated. Resultantly, it is feared that data will be a gain written onto the data written by the different device, destroying the data.